1. Field of the Invention
The present invention relates to a nitride semiconductor light emitting device.
2. Description of the Related Art
A light emitting device using a gallium nitride type compound semiconductor material can emit light of a wide range of wavelengths from blue to orange by adjusting the composition of each compound semiconductor layer. FIG. 12 illustrates a conventional nitride semiconductor light emitting device 1200 using a GaN substrate as disclosed in Japanese Laid-Open Publication No. 7-94784. First, a GaN substrate 33 is produced through a CVD method with materials such as Ga, HCl, NH3, and the like. Then, an n-GaN layer 34, an InGaN light emitting layer 35, and a p-GaN layer 36 are deposited on the GaN substrate 33, thereby providing a layered structure. Electrodes 31 and 32 are respectively provided on the outermost layers of the layered structure.
However, with such a conventional technique, it is not possible to obtain a light emitting diode having an improved emission efficiency or a semiconductor laser device having a reduced threshold current (i.e., a prolonged operating lifetime). There has been a demand for a novel technique for obtaining a light emitting diode having an improved emission efficiency and a prolonged operating lifetime.
According to one aspect of this invention, there is provided a nitride semiconductor light emitting device, including: a GaN substrate into which a group VII element is doped; an intermediate layer section provided on the GaN substrate; and a light emitting layer provided on the intermediate layer section. The intermediate layer section has a sufficient thickness to prevent the group VII element diffused from the GaN substrate from being detected in the light emitting layer.
In one embodiment of the invention, the thickness of the intermediate layer section is equal to or greater than about 0.2 xcexcm.
In one embodiment of the invention, the group VII element has a concentration in a range of about 1xc3x971016 cmxe2x88x923 to about 1xc3x971020 cmxe2x88x923.
In one embodiment of the invention, the intermediate layer section comprises a layer into which a group IV element or a group VI element is doped in a range of about 1xc3x971017 cmxe2x88x923 to about 1xc3x971020 cmxe2x88x923.
In one embodiment of the invention, the group VII element is Cl.
In one embodiment of the invention, the GaN substrate is an n-type substrate, and the dopant for the Intermediate layer section is an n-type dopant.
In one embodiment of the invention, the intermediate layer section comprises a plurality of doped nitride semiconductor layers, and one of the plurality of doped nitride semiconductor layers closest to the GaN substrate has a dopant concentration which is greater than that of another one of the plurality of doped nitride semiconductor layers closest to the light emitting layer.
In one embodiment of the invention, the nitride semiconductor light emitting device is a semiconductor laser device; the intermediate layer section comprises a plurality of layers including an n-InGaN base layer, an n-AlGaN cladding layer and an n-InGaN guide layer, which are arranged in this order from the GaN substrate side; and the intermediate layer section has a total thickness equal to or greater than about 0.5 xcexcm.
In one embodiment of the invention, a dopant concentration in the n-AlGaN cladding layer and the n-InGaN guide layer of the intermediate layer section is equal to or greater than about 1xc3x971017 cmxe2x88x923 and less than or equal to about 1xc3x971019 cmxe2x88x923.
In one embodiment of the invention, the n-AlGaN cladding layer has a thickness less than or equal to about 1.5 xcexcm.
In one embodiment of the invention, the nitride semiconductor light emitting device is a semiconductor laser device; the Intermediate layer section comprises a plurality of layers including an n-InGaN base layer, an n-AlGaInN cladding layer and an n-InGaN guide layer, which are arranged in this order from the GaN substrate side; and the intermediate layer section has a total thickness equal to or greater than about 0.5 xcexcm.
In one embodiment of the invention, a dopant concentration in the n-AlGaInN cladding layer and the n-InGaN guide layer of the intermediate layer section is equal to or greater than about 1xc3x971017 cmxe2x88x923 and less than or equal to about 1xc3x971019 cmxe2x88x923.
In one embodiment of the invention, the n-AlGaInN cladding layer has a thickness less than or equal to about 1.5 xcexcm.
Thus, the invention described herein makes possible the advantage of providing a light emitting device using a gallium nitride type compound semiconductor material having an improved emission efficiency and a prolonged operating lifetime.